Radiative QED corrections to the lepton anomaly from four-loop vacuum polarization insertions with three identical leptons

Abstract

Analytical expressions for the tenth order electromagnetic corrections to the lepton ($L=e,\hat{I}¼$ and $\ddot{I}„$) anomaly $a_L$ are derived explicitly for a class of Feynman diagrams with insertions of the vacuum polarization operator consisting of four closed lepton loops. We consider a particular case when one loop is formed by the lepton $L$ of the same kind as the one under consideration, the other three loops being formed by leptons $\ell \ne L$. The method is based on the consecutive application of dispersion relations for the polarization operator and the Mellin--Barnes transform for the propagators of massive particles. The result is expressed in terms of the mass ratio $r=m_{\ell }/m_L$. We investigate the behaviour of the exact analytical expressions as $r\to 0$ and $r\to \infty$ and compare them with the corresponding asymptotic expansions known in the literature.

18 pages, 4 eps figure. Talk presented at the Scientific session of Nuclear Physics section of Physics Division of RAS, April 1-5, Physics of Fundamental Interactions